JP2009199027A - Charging device, process cartridge having the same, and image forming apparatus having the process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging device capable of effectively cleaning a contaminant stuck to the surface of a charging member and maintaining the cleaning performance over a long period of time. <P>SOLUTION: The charging device 90 has a cylindrical cleaning member 91 fixed in a corotated manner to the charging member (a charging roller) 9 to clean the surface of the charging member 9. (A) The cleaning member 91 is composed of a resin foam 909 having an open cell structure, and corotation assisting parts 910 formed at both ends and having a static friction coefficient of 1.0 or more. (B) The corotation assisting parts 910 abut on the portions, corresponding to image non-forming parts of a photoreceptor drum 2Y, of the charging member 9. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a charging device used in an image forming apparatus such as a copying machine, a laser beam printer, and a facsimile, a process cartridge having the charging device, and an image forming apparatus having the process cartridge.

  In a conventional electrophotographic image forming apparatus such as an electrophotographic copying machine, a laser printer, and a facsimile, a charging device that performs a charging process on an image carrier (photosensitive drum) is used. FIG. 7 is an explanatory diagram of an electrophotographic image forming apparatus having a conventional charging roller.

  In FIG. 7, reference numeral 130 denotes a conventional electrophotographic image forming apparatus. A conventional electrophotographic image forming apparatus 130 includes a photosensitive drum 111 on which an electrostatic latent image is formed, a charging member (charging roller) 112 that performs charging processing in contact with the photosensitive drum 111, and exposure of laser light and the like. Means 113, a toner carrier (developing roller) 114 for attaching toner 115 to the electrostatic latent image on the photosensitive drum 111, and a transfer member (transfer roller) 116 for transferring the toner image on the photosensitive drum 111 onto the recording paper 117. And a cleaning member (cleaning blade) 118 for cleaning the photosensitive drum 111 after the transfer process. In FIG. 7, reference numeral 119 denotes waste toner from which the toner 115 remaining on the surface of the photosensitive drum 111 is removed by the cleaning member 118, 120 is a developing device, and 121 is a cleaning device. . In FIG. 7, functional units normally required in other electrophotographic processes are omitted because they are not required in this case.

  Next, a basic image forming operation of the conventional electrophotographic image forming apparatus 130 will be described.

  When a DC voltage is supplied from a power pack (not shown) to the charging roller 112 in contact with the photosensitive drum 111, the surface of the photosensitive drum 111 is uniformly charged to a high potential. Immediately thereafter, when image light is irradiated onto the surface of the photosensitive drum 111 by the exposure unit 113, the potential of the irradiated portion of the photosensitive drum 111 decreases. It is known that such a charging mechanism to the surface of the photosensitive drum 111 by the charging roller 112 is a discharge according to Paschen's law in a minute space between the charging roller 112 and the photosensitive drum 111.

  Since the image light has a light amount distribution according to white / black of the image, when the image light is irradiated, the potential distribution corresponding to the recorded image on the surface of the photosensitive drum 111 by the irradiation of the image light, that is, An electrostatic latent image is formed. When the portion of the photosensitive drum 111 on which the electrostatic latent image is thus formed passes through the developing roller 114, toner adheres according to the level of the potential, and a toner image that visualizes the electrostatic image is formed. Is done. The recording paper 117 is conveyed by a registration roller (not shown) at a predetermined timing to the portion of the photosensitive drum 111 where the toner image is formed, and overlaps the toner image. Then, after the toner image is transferred onto the recording paper by the transfer roller 116, the recording paper 117 is separated from the photosensitive drum 111. The separated recording paper 117 is conveyed through a conveyance path, heated and fixed by a fixing unit (not shown), and then discharged outside the apparatus. When the transfer is completed in this manner, the surface of the photosensitive drum 111 is cleaned by the cleaning member 118, and the residual charge is removed by a quenching lamp (not shown), so that the next image forming process is performed. Prepared for.

  In the conventional image forming apparatus as described above, as a method of charging the surface of the image bearing member (photosensitive member), in recent years, a charging roller formed in a roller shape with a conductive member is brought close to the surface of the photosensitive member. A charging device that charges the surface of the photoconductor by applying a voltage between the charging roller and the photoconductor in this state has the advantage of reducing ozone and power consumption. It has become.

  However, the transfer residual toner remaining on the surface of the photoconductor after the toner image transfer is not completely removed in the cleaning process, and these transfer residual toners adhere to the charging roller when reaching a region close to or in contact with the charging roller. There was a problem to do. If the transfer residual toner is a normal polarity toner that is charged to the same polarity as the charged polarity, the toner that is charged to the opposite polarity without being charged to the normal polarity when stirred with the developer. In other words, so-called reversely charged toner exists. If the toner is charged to a normal polarity, the toner and the charging roller will repel electrostatically and will not adhere to the surface, but the reversely charged toner will attract electrostatically and adhere to the surface of the charging roller. Will be. In addition to the reversely charged toner, for example, if dust such as paper dust is charged and electrostatically attracts the charging roller, it adheres.

  In recent years, with increasing demand for high image quality and high definition of images, toners having a small particle size and a spherical shape have been used in the development process. By using such a toner, the toner is made to adhere precisely to the electrostatic latent image. However, the toner having a small particle size and a spherical shape has a problem that contamination of the surface of the charging roller becomes more serious because it easily slips through the cleaning blade in the cleaning process.

  In order to more uniformly charge the surface of the photoconductor, a method of applying a charging bias in which an alternating current (AC) voltage is superimposed on a direct current (DC) voltage is used. When this AC voltage is superposed, the surface of the photoconductor is roughened by the discharge energy, so that the surface of the photoconductor is worn more. Therefore, in order to prevent the surface of the photoconductor from being worn, a method of protecting the surface of the photoconductor by applying a lubricant such as a fatty acid metal salt to the surface of the photoconductor is used. In this way, applying the lubricant to the surface of the photoconductor also leads to a reduction in the coefficient of friction on the surface of the photoconductor, and also improves the transfer rate of the toner image and cleaning of the residual toner with a cleaning blade. It also works in the direction of making it happen.

  However, since a thin layer of lubricant provided on the surface of the photosensitive member is easily supplemented with hard external additive particles such as silica released from the toner, these external additive particles adhere to the contact surface of the cleaning blade. There is a problem that the edge of the cleaning blade is damaged when it passes through, and that the cleaning blade is chipped or worn. As the cleaning blade wears, the amount of toner that passes through the blade also increases, increasing the surface contamination of the charging roller. Furthermore, since the lubricant itself is decomposed by the discharge energy of the charging bias and electrostatically attracts the charging roller and adheres to the charging roller, contamination of the surface of the charging roller becomes more serious.

  Therefore, as described above, the surface of the charging roller needs to be cleaned in order to prevent the toner passing through the cleaning blade from adhering to the charging roller to prevent uniform charging of the surface of the photoreceptor.

  As a cleaning member for the charging roller, a sponge member such as foamed polyurethane or foamed polyethylene (see Patent Document 1) or a brush roller (see Patent Document 2) is used. These cleaning members are brought into contact with the surface of the charging roller so as to be slid to remove deposits such as toner. The adhering material such as toner is collected in the internal pores in the case of a sponge material, and is accumulated between the fibers of the brush in the case of a brush roller. However, since there is a limit to the amount of deposits accumulated in these cleaning members, there remains a problem in maintaining the cleaning performance of the cleaning member over a long period of time. For example, in a process cartridge including a charging roller, it is necessary to maintain the cleaning performance of the charging roller in accordance with the life of other components. Is not enough.

  Therefore, in place of the cleaning member, it has been proposed to use a cleaning member made of a melamine resin foam having an open-cell structure as one that can maintain the performance of the charging roller over a long period of time (see Patent Documents 2 and 3). .) According to these cleaning members, dirt is not clogged in one pore as in the case of a conventional sponge material, so that the cleaning function of the surface of the charging roller can be maintained for a long time.

  However, the present inventors have studied the above-mentioned cleaning member. As a result, although the roller surface contamination is reduced as compared with the conventional case, the cleaning performance is not perfect. Found out that it was going on. Then, the present inventors searched for the cause of such contamination of the roller surface, and in the case where the cleaning member is brought into contact with the charging roller by its own weight or pressure applying means. Finds that a slip occurs between the cleaning member and the charging roller, so that an adhering substance such as toner is rubbed and fused on the surface of the charging roller, which causes roller surface contamination. It was.

  Conventionally, as the charging roller, a material in which an elastic body such as rubber or elastomer in which a conductive material is dispersed is coated around the core metal has been used. In particular, in a charging device in which the image carrier (photosensitive member) and the charging roller are close to each other in a non-contact manner, the gap between the photosensitive member and the charging roller changes with time. There has been a problem that image unevenness due to change occurs. Therefore, it has been found that it is effective to change the charging roller to an elastic body such as rubber or elastomer and to use an inelastic body such as a thermoplastic resin.

However, in an image forming apparatus having a charging roller formed using an inelastic body, the charging roller formed using an inelastic body has a high hardness, so that slippage with the cleaning member is more likely to occur. For this reason, there is a problem that adhesion of adherents such as toner to the roller surface is likely to occur, and therefore contamination of the roller surface becomes more serious.
JP-A-5-297690 Japanese Patent Laid-Open No. 7-140763 JP 2005-70750 A Japanese Patent Laid-Open No. 2005-221981

  The present invention aims to solve this problem.

  That is, the present invention can effectively clean contaminants adhering to the surface of the charging member and can maintain the cleaning performance for a long period of time, a process cartridge having the same, and a process thereof An object of the present invention is to provide an image forming apparatus having a cartridge.

In order to achieve the above object, the invention described in claim 1 is provided on a conductive support, an electrical resistance adjustment layer formed on the conductive support, and both ends of the electrical resistance adjustment layer. A chargeable member having a gap retaining member, and a surface of the charging member that is pressed against the charging member by its own weight or pressure applying means and is fixed so as to rotate with the charging member. A charging device having a cylindrical cleaning member for cleaning
(A) The cleaning member is composed of a resin foam having an open-cell structure, and a follow-up auxiliary portion formed at both ends thereof having a static friction coefficient of 1.0 or more, and
(B) In the charging device, the follow-up auxiliary portion is in contact with a portion corresponding to a non-image forming portion of the photosensitive drum in the charging member.

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, the resin foam having the open cell structure is composed of a melamine resin.

  The invention described in claim 3 is characterized in that, in the invention described in claim 1 or 2, the resin foam having the open cell structure is heated and compressed from the original shape.

  The invention described in claim 4 is characterized in that, in the invention described in any one of claims 1 to 3, the follow-up auxiliary portion is made of an elastic material.

  The invention described in claim 5 is the invention described in claim 4, wherein the elastic material is an elastic material obtained by subjecting a melamine resin foam impregnated with rubber and a crosslinking agent to a crosslinking reaction treatment. It is characterized by that.

  The invention described in claim 6 is the thermoplastic resin according to any one of claims 1 to 5, wherein the electrical resistance adjusting layer is obtained by dispersing a polymer type ion conductive agent in a thermoplastic resin. It is characterized by comprising.

The invention described in claim 7 is the invention described in any one of claims 1 to 6, wherein the volume resistivity value of the electric resistance adjusting layer is 10 ⁶ to 10 ⁹ Ω · cm. It is a feature.

  The invention described in claim 8 is characterized in that, in the invention described in any one of claims 1 to 7, a surface layer is provided on a surface of the electric resistance adjusting layer. is there.

  The invention described in claim 9 is characterized in that, in the invention described in claim 8, the resistance value of the surface layer is larger than the resistance value of the electric resistance adjusting layer.

  According to a tenth aspect of the present invention, there is provided a process cartridge including at least an image carrier that forms a latent image and a charging device, and is integrally supported and detachably fixed to a main body of the image forming apparatus. A process cartridge comprising the charging device according to any one of claims 1 to 9.

  According to an eleventh aspect of the present invention, there is provided a process cartridge, exposure means for exposing the surface of the image carrier to form an electrostatic latent image, and supplying toner to the electrostatic latent image on the surface of the image carrier. An image forming apparatus comprising at least developing means for visualizing and transferring means for transferring a visualized image of the surface of the image carrier onto a transfer medium, wherein the process cartridge is constituted by the process cartridge according to claim 10. An image forming apparatus.

  According to the first aspect of the present invention, the conductive support, the electrical resistance adjustment layer formed on the conductive support, and the gap holding members provided at both ends of the electrical resistance adjustment layer are provided. A charging member (charging roller) is pressed against the charging member by its own weight or pressure applying means, and the surface of the charging member fixed to rotate with the charging member is cleaned. In the charging device having a cylindrical cleaning member, (a) the cleaning member is a resin foam having an open cell structure, and a follow-up auxiliary portion having a static friction coefficient of 1.0 or more formed at both ends thereof And (b) the rotation assisting portion is in contact with a portion of the charging member corresponding to the non-image forming portion of the photosensitive drum, so that the cleaning member is charged. Slip against the material (charging roller) can be prevented, and the adhering material such as toner can be prevented from being rubbed and fused on the surface of the charging roller, and therefore adhered to the surface of the charging member. It is possible to provide a charging device capable of effectively cleaning contaminants and maintaining the cleaning performance for a long period of time.

  According to the second aspect of the invention, since the resin foam having the open cell structure is composed of melamine resin, the open cell structure can be easily formed. The resin foam having the open cell structure can be prevented from staying in the bubbles, and thus the cleaning performance can be maintained for a longer period.

  According to the invention described in claim 3, since the resin foam is heat-compressed from the original shape, it is possible to prevent the deterioration of the cleaning property at the pinhole portion generated in the non-compressed resin foam. The cleaning performance can be maintained for a longer period of time.

  According to the invention described in claim 4, since the accompanying auxiliary portion is made of an elastic material, it is possible to further prevent the cleaning member from slipping, and to maintain the cleaning performance for a long time. Can do.

  According to the invention described in claim 5, since the elastic material is formed of an elastic material obtained by subjecting a melamine resin foam impregnated with rubber and a crosslinking agent to a crosslinking reaction treatment, the friction coefficient is 1 It is possible to easily form a rotation assisting portion of 0.0 or more, and therefore, it is possible to further prevent the cleaning member from slipping. Therefore, the cleaning performance can be maintained for a longer period of time.

  According to the invention described in claim 6, since the electric resistance adjusting layer is composed of a thermoplastic resin in which a polymer type ion conductive agent is dispersed in a thermoplastic resin, a resin composition in which a conductive pigment is dispersed. It is possible to effectively prevent variation in electrical resistance value and bleed-out caused by poor dispersion as seen in objects.

According to the invention described in claim 7, since the volume resistivity value of the electric resistance adjusting layer is 10 ⁶ to 10 ⁹ Ω · cm, sufficient charging ability and transfer ability can be ensured, Occurrence of abnormal discharge due to power concentration on the image carrier can be prevented, and a uniform image can be obtained for them.

  According to the invention described in claim 8, since the surface of the electric resistance adjusting layer is provided with a surface layer, the toner and the additive added to the toner can be charged for a long time. Can be prevented from adhering to the surface.

  According to the ninth aspect of the present invention, since the resistance value of the surface layer is larger than the resistance value of the electric resistance adjusting layer, it is possible to prevent voltage concentration and abnormal discharge from occurring on the defective portion of the image carrier. it can.

  According to a tenth aspect of the present invention, a process cartridge includes at least an image carrier that forms a latent image and a charging device, and is integrally supported and detachably fixed to a main body of the image forming apparatus. In the above, since the charging device is constituted by the charging device according to claims 1 to 9, stable image quality can be obtained over a long period of time, and replacement can be simplified by user maintenance.

  According to the eleventh aspect of the present invention, the process cartridge, the exposure means for exposing the surface of the image carrier to form an electrostatic latent image, and supplying the toner to the electrostatic latent image on the surface of the image carrier. 11. The image forming apparatus comprising at least a developing unit that visualizes and a transfer unit that transfers a visualized image of the surface of the image carrier onto a transfer medium, wherein the process cartridge includes the process cartridge according to claim 10. Therefore, high image quality can be obtained and a stable image can be obtained over a long period of time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing a state in which a charging member (charging roller) showing an embodiment of the present invention is arranged on an image carrier. FIG. 2 is a schematic explanatory view of an image forming apparatus showing an embodiment of the present invention. FIG. 3 is a schematic explanatory diagram showing the configuration of the image forming unit in the image forming apparatus showing an embodiment of the present invention. FIG. 4 is a schematic diagram showing an example of measurement of the static friction coefficient by the Euler belt method. FIG. 5 is a partial view of the recording paper, where (a) shows that the recording paper is not soiled due to no contamination on the charging roller, and (b) is the charging roller. This indicates that vertical streaks were formed on the recording paper due to the occurrence of contamination. FIG. 6 shows the relationship between the slip time from when the charging roller starts to rotate until the cleaning member starts following the rotation of the charging roller and the static friction coefficient of the cleaning member rotation assisting portion. It is a graph to show.

  In FIG. 1, reference numeral 90 denotes a charging device. The charging device 90 includes a conductive support (core metal) 903, an electric resistance adjustment layer 902 formed on the conductive support 903, and a gap holding portion 904 provided at both ends of the electric resistance adjustment layer 902. A charging member (charging roller) 9 having pressure and a pressure contact with the charging member 9 by its own weight or pressure applying means (compression spring) 908, and fixed so as to rotate with the charging member 9. And a cylindrical cleaning member 91 for cleaning the surface of the charging member 9. In the charging device 90, (a) the cleaning member 91 includes a resin foam 909 having an open cell structure, and a follow-up assisting portion 910 having a static friction coefficient of 1.0 or more formed at both ends thereof. And (b) the rotation assisting portion 910 is in contact with a portion of the charging member 9 corresponding to the non-image forming portion of the photosensitive drum 2Y. In FIG. 1, reference numeral 901 denotes a surface layer, reference numeral 905 denotes a bearing, and reference numeral 907 denotes pressure applying means (compression spring) that presses the gap holding member 904 against the image carrier 2Y.

  As described above, the conductive support (core metal) 903, the electric resistance adjustment layer 902 formed on the conductive support 903, and the gap holding members 904 provided at both ends of the electric resistance adjustment layer 902 are provided. A charging member (charging roller) 9 having a self-weight or pressure applying means (compression spring) 908 pressed against the charging member 9 and fixed so as to rotate with the charging member 9; In the charging device 90 having a cylindrical cleaning member 91 for cleaning the surface of the charging member 9, (a) the cleaning member 91 is formed on the both ends of the resin foam 909 having an open cell structure. And (b) the follower assisting part 910 is a photosensitive drum driver in the charging member 9. When the cleaning member 91 is in contact with a portion corresponding to a non-image forming portion of 2Y, the cleaning member 91 is prevented from slipping against the charging member (charging roller) 9, and a deposit such as toner is rubbed on the surface of the charging member 9. It can be prevented from being attached and fused, so that contaminants adhering to the surface of the charging member 9 can be effectively cleaned and the cleaning performance can be maintained over a long period of time. A charging device 90 that can be provided can be provided.

  As shown in FIG. 1, the cleaning member 91 rotates with the rotation of the charging member (charging roller) 9 in the direction of the arrow. As described above, when the cleaning member 91 is driven by the rotation of the charging roller 9, a driving device is not necessary for the cleaning member 91, so that the configuration can be simplified.

  In the present invention, the resin foam 909 having the open cell structure is preferably composed of a melamine resin. As described above, when the resin foam 909 having the open cell structure is made of melamine resin, the open cell structure can be easily formed. Therefore, the material has the open cell structure of the substance attached to the charging member 9. Resin foam 909 can be prevented from staying in the bubbles, so that the cleaning performance can be maintained for a longer period of time.

As the physical properties of the resin foam 909, the density of at least the contact portion with the charging roller 9 is preferably 5 kg / m ³ or more, and the tensile strength is preferably 1.2 kg / cm ^2. That's it. If the density of the contact portion with the charging roller 9 is less than 5 kg / m ³ , the contact surface with the charging member (charging roller) 9 is too small, so that a sufficient cleaning performance cannot be obtained. In this case, a charging failure occurs, and thus a defect such as background smearing occurs in the image. Further, if the tensile strength is less than 2 kg / cm ² , the strength is not sufficient, and therefore the resin foam 909 becomes tattered at an early stage, and thus the cleaning performance is not exhibited. Therefore, among the resin foams 909 showing the physical property values, those made of melamine resin are particularly preferable. Since the resin foam 909 made of melamine resin is hard in mesh-like fibers, the deposit on the charging roller 9 can be easily scraped off or can be removed by hooking. As described above, the charging device 90 of the present invention has the cleaning member 91 excellent in cleaning performance and exhibits a brittle property as described above. Therefore, the fresh surface of the cleaning member 91 is always in contact with the surface of the charging roller 9. Therefore, good cleaning performance can be maintained.

   Since the resin foam 909 made of the melamine resin has variations in the expansion ratio, there are many pinholes of about φ1 to 3 mm on the surface. The presence of such pinholes reduces the contact area with the charging roller 9 to be cleaned, partially causes defective cleaning, and causes uneven charging. Therefore, when the melamine resin foam is heated and compressed in the above compression rate range, the open-cell structure can be made dense, and therefore the cleaning performance can be improved.

  Therefore, in the present invention, the resin foam 909 is preferably heated and compressed from its original shape. As described above, when the resin foam 909 is heated and compressed from the original shape, it is possible to prevent deterioration of the cleaning performance at the pinhole portion that occurs in the non-compressed resin foam 909. Can be maintained over time.

The compression ratio of the resin foam 909 constituting the cleaning member 9 is preferably 30% or more. The compression rate is expressed by the following formula: compression rate (%) = {(diameter before compression−diameter after compression) / diameter before compression} × 100
Sought by.

  In the present invention, the accompanying auxiliary portion 910 is preferably made of an elastic material. As described above, when the accompanying auxiliary portion 910 is made of an elastic material, it is possible to further prevent the cleaning member 91 from slipping. Therefore, the cleaning performance can be maintained over a long period of time.

  In the present invention, the elastic material is preferably composed of an elastic material obtained by subjecting a melamine resin foam impregnated with rubber and a crosslinking agent to a crosslinking reaction treatment. Thus, when the elastic material is made of an elastic material obtained by subjecting a melamine resin foam impregnated with rubber and a cross-linking agent to a cross-linking reaction treatment, a follow-up auxiliary portion having a friction coefficient of 1.0 or more is provided. The cleaning member 91 can be more easily prevented from slipping, so that the cleaning performance can be maintained for a longer period of time.

  The cleaning member 91 has a cylindrical shape. Thus, when the cylindrical cleaning member 91 is rotatably attached, the surface to be cleaned can be always changed, and a resin foam 909 made of melamine resin is wound around the core metal 903 in a cylindrical shape. Can be formed.

  A method for manufacturing the charging cleaning member will be described below.

  After the resin foam composed of melamine resin is heated and compressed, a cored bar is inserted, and then the outer diameter is adjusted by means such as polishing. Then, both ends are impregnated with a low molecular weight rubber and a cross-linking agent by means such as dipping, and a cross-linking reaction is performed to form a rubbery substance, thereby forming a follow-up auxiliary part. In order to improve the outer diameter accuracy of the follow-up auxiliary portion formed in this way, polishing may be performed after the impregnation. The rubber may be any of natural rubber, butadiene rubber, hydrin rubber, styrene-butadiene rubber, nitrile rubber, ethylene-propylene rubber, butyl rubber, silicone rubber, urethane rubber, fluorine rubber, chlorine rubber, thermoplastic elastomer, etc., and has a friction coefficient. High urethane rubber or the like is preferable. In order to improve workability such as dipping, various rubbers may be diluted with an organic solvent or the like. The crosslinking agent is not particularly limited, and a curing agent such as an isocyanate resin, a melamine resin, or a guanamine resin, or a substance such as sulfur, an organic sulfur-containing compound, or a peroxide can be appropriately selected.

  In the present invention, the electric resistance adjusting layer 902 is preferably made of a thermoplastic resin in which a polymer ion conductive agent is dispersed in a thermoplastic resin. As described above, when the electrical resistance adjusting layer 902 is made of a thermoplastic resin in which a polymeric ionic conductive agent is dispersed in a thermoplastic resin, a dispersion as seen in a resin composition in which a conductive pigment is dispersed is used. It is possible to effectively prevent variation in electrical resistance value and bleed-out due to defects.

In the present invention, the volume resistivity value of the electric resistance adjusting layer 902 is preferably 10 ⁶ to 10 ⁹ Ω · cm. As described above, when the volume resistivity value of the electric resistance adjusting layer 902 is 10 ⁶ to 10 ⁹ Ω · cm, sufficient charging ability and transfer ability can be secured, and power to the image carrier 2Y can be secured. Occurrence of abnormal discharge due to concentration can be prevented, and a uniform image can be obtained for them.

  In the present invention, a surface layer 901 is preferably provided on the surface of the electric resistance adjusting layer 902. As described above, when the surface layer 901 is provided on the surface of the electric resistance adjusting layer 902, the toner and the additive added to the toner adhere to the surface of the charging member 9 over a long period of time. Can be prevented.

  In the present invention, the resistance value of the surface layer 901 is preferably larger than the resistance value of the electric resistance adjusting layer 902. As described above, when the resistance value of the surface layer 901 is larger than the resistance value of the electric resistance adjusting layer, it is possible to prevent voltage concentration and abnormal discharge from occurring on the defective portion of the image carrier 2Y.

  Next, the charging device 90 will be described in detail. As shown in FIG. 1, the charging device 90 of the present invention includes a cylindrical charging member 9 disposed to face the photosensitive drum 2Y, and a surface opposite to the surface where the charging member faces the photosensitive drum 2Y. It comprises a cylindrical charging cleaning member 91 arranged so as to contact the surface. Further, the charging member 9 is urged at both ends thereof toward the photosensitive drum 2Y by a compression spring 907 which is a pressure applying unit. The charging member 9 is connected to a power source (not shown), and a predetermined voltage is applied thereto. The voltage may be only a direct current (DC) voltage, but is preferably a voltage obtained by superimposing an alternating current (AC) voltage on a DC voltage. By applying the AC voltage, the surface of the photosensitive drum 2Y can be more uniformly charged. The charging member 9 may be provided in contact with the photosensitive drum 2Y. However, in the present embodiment, the charging member 9 is provided with a minute gap G with respect to the photosensitive drum 2Y. The minute gap G abuts the surface of the gap holding member 904 on the surface of the photosensitive drum 2Y, for example, by providing gap holding members 904 having a certain thickness to the non-image forming regions at both ends of the charging member 9. Can be set.

  The minute gap G between the charging member 9 and the photosensitive drum 2Y is set to 100 μm or less, preferably about 5 to 70 μm from the gap holding member. Thereby, formation of an abnormal image at the time of operation of the charging device 90 can be suppressed. When the minute gap G is 100 μm or more, the distance to reach the photosensitive drum 2Y becomes longer, so that the discharge start voltage according to Paschen's law increases, and further, the discharge space to the photosensitive drum 2Y increases. In order to charge the photosensitive drum 2Y to a predetermined level, a large amount of discharge products are required due to discharge, which remains in the discharge space after image formation and adheres to the photosensitive drum 2Y. It becomes a cause of accelerating deterioration with time of 2Y. Further, when the minute gap G is small, the reach distance to the photosensitive drum 2Y is shortened, so that the photosensitive drum 2Y can be charged even if the discharge energy is small. However, the space G formed by the charging member 9 and the photosensitive drum 2Y becomes narrow, and the air flow becomes worse. Therefore, since the discharge product formed in the discharge space stays in this space, it remains in a large amount in the discharge space after image formation and adheres to the photosensitive drum 2Y as in the case where the minute gap G is large. As a result, the deterioration of the photosensitive drum 2Y with time is promoted. Accordingly, it is preferable to reduce the discharge energy to reduce the generation of discharge products and to form a space that does not retain air. Therefore, the micro gap G is preferably 100 μm or less and in the range of 5 to 70 μm. Thereby, the occurrence of streamer discharge can be prevented, the generation of discharge products can be reduced, the amount deposited on the photosensitive drum 2Y can be reduced, and spotted image spots / image flow can be prevented.

  Here, the toner remaining on the photosensitive drum 2Y after development is cleaned by the cleaning device 64 provided facing the photosensitive drum 2Y. However, it is difficult to completely remove the toner, and a very small amount of toner is removed. It passes through the cleaning device 64 and is conveyed to the charging device 90. At this time, if the particle diameter of the toner is larger than the minute gap G, the toner may be rubbed by the photosensitive drum 2Y or the charging member 9 and heated, and may be fused to the charging member 9. The portion where the toner is fused is close to the photosensitive drum 2Y, and thus abnormal discharge occurs preferentially. Therefore, the minute gap G is preferably larger than the maximum particle size of the toner used in the image forming apparatus 1.

  As shown in FIGS. 1 and 3, the charging member 9 is fitted to a bearing provided on a side plate of a housing (not shown) of the charging device, and is provided on a bearing 905 made of a resin having a low coefficient of friction that is not driven by the bearing. 907 is pressed toward the surface of the photosensitive drum. As a result, a certain minute gap G can be formed even if there is mechanical vibration and deviation of the metal core 903. The pressing load is preferably 4 to 25N, and more preferably 6 to 15N. Even if the charging member 9 is fixed by the bearing 905, the size of the minute gap G may fluctuate due to vibration during operation and unevenness of the surface of the charging member, and the minute gap G may deviate from an appropriate range. Therefore, the deterioration of the photosensitive drum 2Y is promoted over time. Here, the load means all loads applied to the photosensitive drum 2Y through the gap holding member 904. This can be adjusted by the force of the compression springs 907 provided at both ends of the charging member 9, the self weight of the charging member 9 and the cleaning member 91, and the like. If the load is small, fluctuation due to rotation of the charging member 9 and jumping up due to impact force of the driving gear or the like cannot be suppressed. When the load is large, the friction between the charging member 9 and the bearing 905 to be fitted increases, and the amount of wear over time is increased to promote fluctuation. Accordingly, the load is preferably in the range of 4 to 25 N, and more preferably in the range of 6 to 15 N, so that the minute gap G is set in an appropriate range, and the generation of discharge products is reduced to the photosensitive drum 2Y. It is possible to extend the life of the photosensitive drum 2Y by reducing the amount of accumulation, and to prevent spot-like abnormal images / image flows.

  As shown in FIGS. 1 and 3, the charging member 9 has a cylindrical shape, and both ends are rotatably supported by gears or bearings 905. In this way, when the charging member 9 is formed with a curved surface gradually separating from the closest part to the image carrier 2Y in the moving direction of the photosensitive drum (image carrier) 2Y, the image carrier 2Y can be more uniformly charged. If the charging member 9 facing the image carrier 2Y has a sharp portion, the potential of that portion becomes high, so that discharge is preferentially started, and it becomes difficult to uniformly charge the image carrier 2Y. Therefore, the image bearing member 2Y can be charged uniformly by having a cylindrical shape and a curved surface. Further, the discharging surface of the charging member 9 is subjected to strong stress. Since the discharge always occurs on the same surface, its deterioration is promoted and may be scraped off. Therefore, if the entire surface of the charging member 9 can be used as a discharging surface, it can be used for a long period of time by rotating it to prevent early deterioration.

  Next, the gap holding member 904, the electric resistance adjusting layer 902, and the surface layer 901 constituting the charging member (charging roller) 9 will be described in detail.

<About the gap holding member 904>
A necessary characteristic of the gap holding member 904 is to form the minute gap G with the photoreceptor 2Y stably over the environment and for a long time (time). For this purpose, the hygroscopicity and the wear resistance are small. Material is desirable. In addition, it is important that the toner and the toner additive do not easily adhere to each other, and that the photosensitive member 2Y is not abraded because it contacts and slides on the photosensitive member 2Y, and is appropriately selected according to various conditions. It is what is done. Specific examples of the material constituting the gap holding member 904 include polyethylene (PE), polypropylene (PP), polyacetal (POM), polymethyl methacrylate (PMMA), polystyrene (PS), and their co-weights. General-purpose resins such as coalesced (AS, ABS), polycarbonate (PC), urethane, fluorine (PTFE) and the like can be mentioned. In particular, in order to securely fix the gap holding member 904, an adhesive can be applied and bonded. The gap holding member 904 is preferably an insulating material and preferably has a volume resistivity of 10 ⁻¹³ Ωcm or more. The reason why insulation is necessary is to eliminate the occurrence of leakage current with the photoreceptor 2Y. The gap holding member 904 is formed by a molding process.

  A part of the gap holding member 904 has a height difference from the electric resistance adjusting layer 902. As a method of forming the minute gap G, it can be formed by simultaneously processing the electric resistance adjusting layer 902 and the gap holding member 904 by removal processing such as cutting and grinding. By simultaneously processing the gap holding member 904 and the electric resistance adjusting layer 902, the gap G can be formed with high accuracy. By forming the height of the portion of the gap holding member 904 adjacent to the electric resistance adjusting layer 902 to be the same as or lower than the height of the electric resistance adjusting layer 902, the contact width between the gap holding member 904 and the photoreceptor 2Y can be reduced. As a result, the gap G between the charging member 9 and the photoreceptor 2Y can be made highly accurate. By doing so, it is possible to prevent the outer surface of the end portion of the gap holding member 904 on the side of the electric resistance adjusting layer 902 from coming into contact with the image carrier 2Y. It is possible to prevent the leakage current from occurring due to the contact of the image carrier 902 with the image carrier 2Y. Further, by processing the end of the gap holding portion 904 on the electric resistance adjustment layer 902 side to be low, this portion can be used as a clearance for the cutting blade or the like when performing the removal processing (escape processing). The shape of the clearance allowance (escape processing) may be any shape as long as the outer surface of the end of the gap holding member 904 is not in contact with the image carrier 2Y. Furthermore, it is difficult to perform masking when coating the surface layer 901 at the boundary between the electric resistance adjusting layer 902 and the gap holding member 904 in consideration of variations. Therefore, when forming the step, the electric resistance adjusting layer is formed. By forming the surface layer 901 up to the gap holding member 904 formed to be the same as or lower than 902, the surface layer 901 can be reliably formed on the electric resistance adjusting layer 902.

<Regarding the electric resistance adjusting layer 902>
The electric resistance adjusting layer 902 is formed of a thermoplastic resin composition in which a polymer type ion conductive material is dispersed. The volume resistivity of the electric resistance adjusting layer 902 is preferably 10 ⁻⁶ to 10 ⁻⁹ Ωcm. If it exceeds 10 ⁻⁹ Ωcm, charging ability and transfer ability are insufficient, and if the volume resistivity is lower than 10 ⁻⁶ Ωcm, leakage due to current concentration on the entire photoreceptor 2Y occurs. The electrical resistance resistance adjusting layer 902 is preferably made of polypropylene (PP), polymethyl methacrylate (PMMA), polystyrene (PS), and copolymers thereof (AS, ABS), polyamide, and polycarbonate (PC). It is comprised with thermoplastic resins, such as. As the polymer type ion conductive material dispersed in these thermoplastic resins, a polymer compound containing a polyether ester amide component is preferable. Polyether ester amide is an ion conductive polymer material, and is uniformly dispersed and immobilized at a molecular level in a matrix polymer. Therefore, there is no variation in resistance value due to poor dispersion as seen in a composition in which an electron conductive conductive agent such as metal oxide or carbon black is dispersed. Further, when a high applied voltage is applied as the charging member (charging roller) 9, in the case of an electron conductive conductive agent, a path through which electricity easily flows locally is formed, so that a leakage current to the image carrier 2 </ b> Y is generated. In the case of the charging member 9, a white / black spot image that is an abnormal image is generated. Since polyether ester amide is a polymer material, bleeding out hardly occurs. About a compounding quantity, since it is necessary to make resistance value into a desired value, it is necessary to make a thermoplastic resin into 20 to 70 weight% and a polymeric ion conductive agent to 80 to 20 weight%.

  Furthermore, an electrolyte (salt) can be added to adjust the resistance value. Examples of salts include alkali metal salts such as sodium perchlorate and lithium perchlorate, lithium imide salts such as lithium bisimide and lithium trismethide, ethyltriphenylphosphonium / tetrafluoroborate, tetraphenylphosphonium / bromide and the like. Grade phosphonium salts. The conductive agent may be used alone or in combination as long as the physical properties are not impaired. In order to uniformly disperse the conductive material in the matrix polymer at the molecular level, by adding a compatibilizing agent, micro-dispersion in the charging material becomes possible. Therefore, a compatibilizing agent may be appropriately used. Examples of the compatibilizing agent include those having a glycidyl methacrylate group which is a reactive group. In addition, an additive such as an antioxidant may be used as long as the physical properties are not impaired. There is no restriction | limiting in particular regarding the manufacturing method of a resin composition, It can manufacture easily by mixing each material, melt-kneading with a biaxial kneader, a kneader, etc. In addition, the electric resistance adjusting layer 902 is formed on the conductive support (core metal) 903 by covering the conductive support 903 with the conductive resin composition 903 by means such as extrusion molding or injection molding. This can be done easily.

<About surface layer 901>
In the present invention, the volume resistivity of the surface layer 901 is larger than the volume resistivity of the electrical resistance adjusting layer 902. As described above, when the volume resistivity of the surface layer 901 is larger than the volume resistivity of the electric resistance adjusting layer 902, voltage concentration and abnormal discharge on the defective portion of the image carrier 2Y can be prevented. . However, if the electric resistance value of the surface layer 901 is too high, the charging ability and the transfer ability are insufficient, so the difference in electric resistance value between the surface layer 901 and the electric resistance adjusting layer 902 should be 10 ³ Ωcm or less. Is preferred. As a material for forming the surface layer 901, a fluorine-based resin, a silicone-based resin, a polyamide resin, a polyester resin, or the like is excellent in non-adhesiveness and is preferable in terms of cleaning properties. Further, the surface layer 901 is formed on the electric resistance adjusting layer 902 by dissolving the constituent material of the surface layer 901 in an organic solvent to prepare a paint, and by various coating methods such as spray coating, dipping, and roll coating. Do. The film thickness is preferably 10 to 30 μm.

  The surface layer material can be either one-component or two-component, but it can improve environmental resistance, non-adhesiveness, and releasability by making it a two-component paint that uses a curing agent. it can. In the case of a two-component paint, a method of crosslinking and curing the resin by heating the coating film is common. However, since the electric resistance adjusting layer 902 is made of a thermoplastic resin, it cannot be heated at a high temperature. As the two-component paint, it is effective to use a main component having a hydroxyl group in the molecule and an isocyanate resin that causes a crosslinking reaction with the hydroxyl group. By using an isocyanate resin, a crosslinking / curing reaction occurs at a relatively low temperature of 100 ° C. or lower. As a result of investigations from the non-adhesiveness of the toner, it was confirmed that the resin is a silicone-based resin having a high non-adhesiveness of the toner, and an acrylic silicone resin having an acrylic skeleton in the molecule is particularly good.

  The charging member (charging roller) 9 has an important electrical characteristic (electrical resistance value), so the surface layer 901 needs to be conductive. As a method for making the surface layer 901 conductive, there is a method of dispersing a conductive agent in a resin material constituting the surface layer. Such a conductive agent is not particularly limited. For example, conductive carbon such as ketjen black EC and acetylene black, rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT. Carbon, color carbon with oxidation treatment, pyrolytic carbon, indium-doped tin oxide (ITO), tin oxide, titanium oxide, zinc oxide, copper, silver, germanium and other metals, and metal oxides, polyaniline , Conductive polymers such as polypyrrole and polyacetylene. In addition, there are ionic conductive materials as conductivity imparting materials, inorganic ionic conductive materials such as sodium perchlorate, lithium perchlorate, calcium perchlorate, lithium chloride, and further ethyltriphenylphosphonium tetrafluoroborate And organic ionic conductive substances such as quaternary phosphonium salts such as tetraphenylphosphonium bromide, modified fatty acid dimethylammonium ethosulphate, ammonium stearate acetate, and laurylammonium acetate.

  As shown in FIGS. 2 and 3, the process cartridge 7 </ b> Y of the present invention includes at least an image carrier 2 </ b> Y that forms a latent image and a charging device 90, and is integrally supported to support the image forming apparatus 1. It is detachably fixed to the main body. And in the process cartridge 7Y of this invention, the said charging device 90 is comprised by the charging device 90 of Claims 1-9. As described above, when the charging device 90 includes the charging device 90 according to claims 1 to 9, stable image quality can be obtained over a long period of time, and replacement can be performed by the user and simplified. The

  As shown in FIGS. 2 and 3, the image forming apparatus 1 of the present invention includes a process cartridge 7Y, an exposure unit L that exposes the surface of the image carrier 2Y to form an electrostatic latent image, and Developing means 11 for visualizing the electrostatic latent image on the surface of the image carrier 2Y by supplying toner, and transfer means (transfer roller) for transferring the visualized image on the surface of the image carrier 2Y to a transfer medium (intermediate transfer belt 3) 25). And in the image forming apparatus 1 of this invention, the said process cartridge 7Y is comprised by the process cartridge of Claim 10. As described above, when the process cartridge 7Y includes the process cartridge according to the tenth aspect, high image quality can be obtained and a stable image can be obtained over a long period of time.

  Next, the image forming apparatus 1 will be described in detail. As shown in FIGS. 2 and 3, the image forming apparatus 1 of the present invention is an endless intermediate transfer belt 3 that is wound around a plurality of support rollers 4, 5, and 6 and rotated in the direction of arrow A. And the first to fourth process cartridges 7Y, 7C, 7M, and 7BK disposed to face the intermediate transfer belt 3. Each of the process cartridges 7Y to 7BK has image carriers 2Y, 2C, 2M, and 2BK configured as drum-like photoreceptors on which toner images of different colors are formed, and differently on the image carriers. Each color toner image is formed and transferred onto the intermediate transfer belt 3 in a superimposed manner. The intermediate transfer belt 3 constitutes an example of a transfer material onto which toner images formed on the image carriers 2Y, 2C, 2M, and 2BK are transferred. The configuration in which the toner image is formed on each of the image carriers 2Y to 2BK of the first to fourth process cartridges 7Y to 7BK and the toner image is transferred to the intermediate transfer belt 3 is substantially different only in the color of the toner image. Since all of them are the same, only a configuration in which a toner image is formed on the image carrier 2Y of the first process cartridge 7Y and transferred to the intermediate transfer belt 3 will be described.

  FIG. 3 is an enlarged cross-sectional view of the first process cartridge 7Y. The image carrier 2Y of the process cartridge 7Y shown here is rotatably supported by the unit case 8 and is driven to rotate clockwise by a driving device (not shown). At this time, a charging voltage is applied to the charging roller 9 rotatably supported by the unit case 8, whereby the surface of the image carrier 2Y is charged to a predetermined polarity. The charged image carrier 2Y is irradiated with light-modulated laser light L emitted from the optical writing device 10 shown in FIG. 2 which is separate from the process cartridge 7Y, and electrostatically is applied to the image carrier 2Y. A latent image is formed. This electrostatic latent image is visualized as a yellow toner image by the developing device 11.

  The developing device 11 has a developing case 12 constituted by a part of the unit case 8, and the developing case 12 contains a two-component dry developer D having toner and a carrier. The developing case 12 includes two screws 13 and 13 for stirring the developer D and a developing roller 23 that is driven to rotate counterclockwise in FIG. The developer pumped up by the toner is carried on the peripheral surface of the developing roller 23, conveyed in the rotation direction of the developing roller 23, and the developer passing through the doctor blade 24 is between the developing roller 23 and the image carrier 2Y. To the development area. At this time, the toner in the developer is electrostatically transferred to the electrostatic latent image formed on the image carrier 2Y, and the latent image is visualized as a toner image. The developer that has passed through the developing region is separated from the developing roller 23 and stirred by the screws 13 and 14. In this way, a toner image is formed on the image carrier 2Y. A developing device using a one-component developer having no carrier can also be employed.

  On the other hand, a primary transfer roller 25 is disposed on the opposite side of the process cartridge 7Y with the intermediate transfer belt 3 interposed therebetween. By applying a transfer voltage to the primary transfer roller 25, the toner image on the image carrier 2Y is changed. Primary transfer is performed on the intermediate transfer belt 3 that is rotationally driven in the direction of arrow A. The transfer residual toner adhering to the image carrier 2Y after the toner image transfer is removed by the cleaning device 26. The cleaning device 26 of this example includes a cleaning case 27 constituted by a part of the unit case 8, a cleaning blade 28 whose tip edge is pressed against the surface of the image carrier 2 Y, and a blade holder that holds the cleaning blade 28. 29 and a toner conveying screw 30 disposed in the cleaning case 27. The cleaning blade 28 is arranged in a counter direction with respect to the surface movement direction of the image carrier 2Y. The cleaning blade 28 is made of an elastic body such as rubber, and the proximal end side of the cleaning blade 28 is fixed to the blade holder 29 by an adhesive, for example. When the leading edge portion of the cleaning blade 28 comes into pressure contact with the surface of the image carrier 2Y, the transfer residual toner on the image carrier 2Y is scraped off and removed. The removed toner is transported out of the cleaning case by a toner transport screw 30 that is driven to rotate. In this way, the cleaning blade 28 serves to clean the image carrier 2Y after the toner image is transferred to the transfer material (the intermediate transfer belt 3 in the example of FIG. 2).

  The process cartridge 7Y is provided with a lubricant application device 31 for applying a lubricant to the image carrier 2Y and a blade 32 having a function of leveling the lubricant applied to the image carrier 2Y. These will be described in detail later.

  In exactly the same manner as described above, a cyan toner image, a magenta toner image, and a black toner image are respectively formed on the second to fourth image carriers 2C, 2M, and 2BK shown in FIG. The yellow toner image is transferred onto the intermediate transfer belt 3 on which the yellow toner image has been transferred, and is primarily transferred to form a composite toner image on the intermediate transfer belt 3. The transfer residual toner on each of the image carriers 2C, 2M, 2BK after the toner image transfer is removed by the cleaning device is the same as in the case of the first image carrier 2Y.

  On the other hand, as shown in FIG. 2, a paper feed cassette 14 containing a recording medium P made of, for example, transfer paper and a paper feed device 16 having a paper feed roller 15 are arranged in the lower part of the image forming apparatus main body 1. The uppermost recording medium P is sent out in the arrow B direction by the rotation of the paper feed roller 15. The fed recording medium is fed by the registration roller pair 17 between the portion of the intermediate transfer belt 3 wound around the support roller 4 at a predetermined timing and the secondary transfer roller 18 disposed on the intermediate transfer belt 3. The At this time, a predetermined transfer voltage is applied to the secondary transfer roller 18, whereby the composite toner image on the intermediate transfer belt 3 is secondarily transferred to the recording medium P. The recording medium P onto which the composite toner image has been secondarily transferred is further conveyed upward and passes through the fixing device 19, and at this time, the toner image on the recording medium P is fixed by the action of heat and pressure. The recording medium P that has passed through the fixing device 19 is discharged to the paper discharge unit 22 at the top of the image forming apparatus 1. Further, the transfer residual toner adhering to the intermediate transfer belt 3 after the toner image transfer is removed by the cleaning device 20.

  The image of this example is controlled so that the wear of the cleaning blade 28 and the image carrier 2Y shown in FIG. 3 is suppressed, and high cleaning performance is maintained by the cleaning blade 28 even when spherical toner having a small particle diameter is used. The forming apparatus is provided with the aforementioned lubricant application device 31. The lubricant application device 31 is also provided in the second to fourth process cartridges 7C, 7M, and 7BK. However, since the configuration and operation are all the same, the process cartridge 7Y shown in FIG. Only the lubricant application device 31 will be described.

  The lubricant application device 31 shown in FIG. 3 includes a brush roller 33 that abuts on the surface of the image carrier 2Y, a solid lubricant 34 that faces the brush roller 33, and a lubricant that fixes and supports the solid lubricant 34. An agent holder 35, a guide 36 for guiding the solid lubricant 34 through the lubricant holder 35, and a compression coil spring 37 which is an example of a pressurizing unit. The brush roller 33 has a core shaft 38 and a large number of brush fibers 39 each having a base end fixed to the core shaft 38. The brush roller 33 extends substantially parallel to the image carrier 2Y and extends along the image carrier 2Y, and the longitudinal ends of the core shaft 38 of the brush roller 33 are not shown in the drawings. The unit case 8 is supported so as to be freely rotatable. During the image forming operation, the brush roller 33 is driven to rotate counterclockwise in FIG. The solid lubricant 34 is formed in a rectangular parallelepiped shape that extends long in parallel with the brush roller 33, and the tip end surface facing the brush roller 33 abuts against the brush fibers 39 of the brush roller 33. The surface on the opposite base end side is fixed to the lubricant holder 35. The guide 36 of the present example has a pair of guide plates 40 and 41 arranged to face each other in parallel with each other, and these guide plates 40 and 41 are integrated by a connecting plate 42. The pair of guide plates 40 and 41 and the connecting plate 42 are constituted by a part of the unit case 8. The lubricant holder 35 is disposed between the pair of guide plates 40 and 41, and the lubricant holder 35 is slidably brought into contact with the mutually opposing surfaces of the guide plates 40 and 41. The method of pressing the lubricant against the brush roller can be achieved by means such as a spring, and the solid lubricant 34 is pressed against the brush roller 33 via the lubricant holder 35. In FIG. 3, this pressing direction is indicated by an arrow C. Instead of the compression coil spring, a pressurizing means including a torsion coil spring or a leaf spring can be used.

  As described above, the solid lubricant 34 is pressed against the brush fibers 39 of the brush roller 33, and the brush fibers 39 are pressed against the surface of the image carrier 2Y. At this time, the brush roller 33 rotates, so that the solid The lubricant of the lubricant 34 is scraped off by the brush fibers 39, and the scraped powdery lubricant is applied to the surface of the image carrier 2Y. As described above, the brush roller 33 constitutes an example of a lubricant supply member that supplies the powdery lubricant scraped from the solid lubricant 34 to the surface of the image carrier. The solid lubricant 34 is scraped off and consumed by the brush roller 33, and its thickness decreases with time. However, since the solid lubricant 34 is pressurized by the compression coil spring 37, the solid lubricant 34 is always brushed. It can abut against the brush fiber 39 of the roller 33.

  Since the lubricant is applied to the surface of the image carrier 2Y, the friction coefficient of the surface of the image carrier can be kept low, thereby suppressing the wear of the image carrier 2Y and the cleaning blade 28, thereby shortening the lifetime. Can be stretched. In addition, even when a spherical toner having a small particle diameter is used, it is possible to prevent the cleaning performance of the image carrier 2Y by the cleaning blade 28 from greatly deteriorating. Further, the lubricant application device 31 is provided with a guide 36, by which the lubricant holder 35 and the solid lubricant 34 are substantially approached or separated from the brush roller 33, that is, the guide 36. The lubricant holder 35 and the solid lubricant 34 are guided so that they can move only in the direction C in which pressure is applied by the compression coil spring 37 and in the opposite direction. For this reason, the solid lubricant 34 does not swing greatly in the direction E perpendicular to this direction. As a result, the solid lubricant 34 can always come into contact with the brush roller 33 in substantially the same area, and a substantially constant amount of lubricant is always supplied to the surface of the image carrier via the brush roller 33, and the image carrier The uneven application of the lubricant to the surface can be prevented.

  In the image forming apparatus 1, as shown in FIG. 3, the lubricant holder 35 contacts the pair of guide plates 40 and 41, and the solid lubricant 34 is guided through the lubricant holder 35. However, the solid lubricant 34 may be guided directly by the guide 36. Further, the solid lubricant 34 is guided by the guide 36 so that the solid lubricant 34 can move substantially only in the direction C approaching or separating from the brush roller 33. It is shown that a certain amount of play may be allowed to move in the direction E perpendicular to the direction C.

  As described above, the lubricant application device 31 includes the lubricant supply member that includes the brush roller 33 that contacts the image carrier 2Y while rotating, the solid lubricant 34 that is opposed to the lubricant supply member, A guide 36 for guiding the solid lubricant 34 and the solid lubricant 34 for supplying the lubricant so that the solid lubricant 34 can move substantially only in a direction approaching or separating from the lubricant supply member. Pressurizing means for pressurizing the member. The image forming apparatus shown in FIG. 3 has a lubricant leveling means configured as a leveling blade 32. The leveling blade 32 is made of an elastic body such as rubber and has a leading edge portion. Is in contact with the surface of the image carrier 2 </ b> Y, and its proximal end is fixed to the holder 45. The leveling blade 32 is arranged in the trailing direction with respect to the moving direction of the image carrier surface. On the other hand, the lubricant supply member composed of the brush roller 33 is disposed downstream of the cleaning blade 28 in the image carrier surface movement direction, as is apparent from FIG.

  According to the image forming apparatus 1 described above, the transfer residual toner adhering to the surface of the image carrier after the transfer of the toner image is removed by the cleaning blade 28, and the brush is applied to the surface of the image carrier 2Y that has become clean by this. A lubricant is applied by the roller 33. Next, when the applied lubricant passes through the leveling blade 32 in contact with the surface of the image carrier, the lubricant is uniformly spread and evenly spread on the surface of the image carrier 2Y. As a result, a lubricant layer having a uniform thickness is formed on the image carrier. As described above, immediately after cleaning the image carrier 2Y, the lubricant is applied and the lubricant is leveled, so that the amount of lubricant applied to the surface of the image carrier and the friction coefficient of the surface thereof are uneven. This can be prevented, and the image quality of the image formed on the recording medium can be improved. In addition, since the leveling blade 32 is arranged in the trailing direction with respect to the moving direction of the image carrier surface, the driving torque of the image carrier 2Y can be prevented from becoming excessively large.

Example 1
A resin composition was prepared by blending 40% by weight of ABS resin (GR-3000, manufactured by Denki Kagaku Kogyo) and 60% by weight of polyetheresteramide (IRGASTAT P18, manufactured by Ciba Specialty Chemicals). 4 parts of polycarbonate-glycidyl methacrylate-styrene-acrylonitrile copolymer (Modiper CL440-G, manufactured by Nippon Oil & Fats) was added to the part, and melted and kneaded to obtain a resin melt composition (volume resistivity: 2 × 10 ⁸ Ωcm). ). Then, this resin melt composition is injection-molded on a support (outer diameter 10 mm) made of SUM22 (Ni plating treatment) to form an electric resistance adjustment layer. After adjusting the thickness, a ring-shaped gap holding member made of high-density polyethylene resin (Novatech PP HY540, manufactured by Nippon Polypro Co., Ltd.) is press-fitted into both ends, and the outer diameter of the gap holding member is 12.5 mm. The outer diameter of the electric resistance adjusting part was simultaneously cut to 12.4 mm to obtain a roller. Next, on the surface of the electric resistance adjusting layer in the roller, an acrylic silicone resin (3000 VH-P, manufactured by Kawakami Paint Co., Ltd.), an isocyanate curing agent, and carbon black (30% by weight with respect to the total solid content) are formed. By spray coating the resin composition (volume resistivity: 2 × 10 ¹⁰ Ωcm) to form a surface layer having a thickness of about 10 μm, a step of about 40 μm is formed between the gap holding member and the surface layer. A charging member (charging roller) was obtained. Subsequently, on the outer peripheral surface of the support (outer diameter 6 mm) made of SUM22 (Ni plating treatment), a layer made of a melamine resin foam (Basotect, manufactured by BASF) was heat-compressed and adhered with an adhesive, The surface was rotationally polished and finished to an outer diameter of 9.5 mm to obtain a roller. A cleaning member is formed by impregnating a rubber-like substance composed of polyether (PEL-20A, manufactured by Nippon Carlit Co., Ltd.) and an isocyanate curing agent at both ends of the roller and heating and compressing it to form a follow-up auxiliary member. (Cleaning roller) was obtained. The compression rate at that time was 30%.

(Example 2)
Except that when forming the follow-up auxiliary member, both ends of the roller were impregnated with a rubbery substance composed of polyether (PEL-AK1, manufactured by Nippon Carlit Co., Ltd.) and an isocyanate curing agent. In the same manner as in No. 1, a charging member (charging roller) and a cleaning member (cleaning roller) were obtained.

(Example 3)
Except for impregnating a rubber-like substance composed of polyether (Neopolynal No. 800, manufactured by Ohashi Chemical Co., Ltd.) and an isocyanate curing agent at both ends of the roller when forming the follow-up auxiliary member. In the same manner as in Example 1, a charging member (charging roller) and a cleaning member (cleaning roller) were obtained.

(Comparative Example 1)
A charging member (charging roller) was obtained in the same manner as in Example 1.

(Comparative Example 2)
Example 1 except that, when the follow-up auxiliary member is formed, both ends of the roller are impregnated with a rubber-like material composed of acrylic silicone (Muki Coat 3000VH, manufactured by Kawakami Paint Co., Ltd.) and an isocyanate curing agent. In the same manner, a charging member (charging roller) and a cleaning member (cleaning roller) were obtained.

(Test 1)
The coefficient of static friction was measured for the follow-up assisting part in each cleaning member obtained in the examples and comparative examples. The measuring method of the coefficient of static friction was performed using the Euler belt method as shown in FIG.

(Test 2)
The charging member (charging roller) and the cleaning member (cleaning roller) obtained in the examples and comparative examples are mounted on the process cartridge shown in FIG. 3, and the image forming apparatus (imageMPC3000) shown in FIG. 2 is used. A continuous image of an image with an image area ratio of 5% (A4 landscape) is output, and a 600 × 2 2 × 2 halftone image A3 is output as an evaluation image every 10000 sheets, and the vertical stripes of the image are generated. Was confirmed visually. FIG. 5 (a) shows that the recording paper cannot be stained due to no contamination on the charging roller, and FIG. 5 (b) shows the recording due to contamination on the charging roller. This indicates that vertical streaks were created on the paper. In this evaluation, in order to accelerate the contamination on the surface of the charging roller, the pressure applied by the compression coil spring 908 was evaluated as normal 5.5N → 8N in order to increase the amount of zinc stearate applied to the photoreceptor surface. . The image printing environment was a normal environment of 23 to 25 ° C. and 30 to 60% RH. In this evaluation, when a vertical streak occurs in an image when the target endurance sheet number of the image forming apparatus is 80000 or less, it is determined that the image is defective (x), and the vertical streak does not occur in the image even if it exceeds 80000. Was judged as good (◯). The evaluation results are shown in the following Table 1.

(Test 3)
As described above, with respect to the charging member (charging roller) and the cleaning member (cleaning roller) obtained in the examples and comparative examples, in the charging device, the cleaning member follows the rotation of the charging roller after the charging roller starts rotating. When the relationship between the slip time required to start the rotation and the static friction coefficient of the rotation assisting portion of the cleaning member was examined, the graph shown in FIG. 6 was obtained. As can be seen from this graph, when the static friction coefficient is less than 1.0, the slip time is 3 ms or more, whereas when the static friction coefficient is 1.0 or more as in the present invention, the static friction coefficient is 2 msec or less. And is stable.

FIG. 2 is a schematic diagram showing a state where a charging roller showing an embodiment of the present invention is arranged on an image carrier. 1 is a schematic explanatory diagram of an image forming apparatus showing an embodiment of the present invention. 1 is a schematic explanatory diagram illustrating a configuration of an image forming unit of an image forming apparatus according to an embodiment of the present invention. It is a schematic diagram which shows an example of the measurement of the static friction coefficient by the Euler belt method. FIG. 4A is a partial view of a recording paper, where (a) shows that the recording roller cannot be soiled due to no contamination on the charging roller, and (b) shows that the charging roller is soiled. This indicates that vertical streaks have been formed on the recording paper. 6 is a graph showing a relationship between a slip time from when the charging roller starts to rotate until the cleaning member follows the rotation of the charging roller and starts rotating, and a static friction coefficient of the rotation assisting portion of the cleaning member. . It is a schematic explanatory drawing of the conventional image forming apparatus.

Explanation of symbols

2Y image carrier (photoconductor, photoconductor drum)
9 Charging member (charging roller)
90 Charging device 91 Cleaning member (cleaning roller)
901 Surface layer 902 Electrical resistance adjustment layer 903 Conductive support (core metal)
904 Gap retaining member 905 Bearing 907 Pressure applying means (compression spring)
908 Pressure applying means (compression spring)
909 Resin foam 910 Rotating auxiliary member G Micro gap

Claims (11)

A conductive support, an electric resistance adjusting layer formed on the conductive support, a charging member having a gap holding member provided at both ends of the electric resistance adjusting layer, and a self-weight or pressure on the charging member And a cylindrical cleaning member that is pressed and abutted by an applying unit and is fixed so as to rotate with respect to the charging member, and that cleans the surface of the charging member.
(A) The cleaning member is composed of a resin foam having an open-cell structure, and a follow-up auxiliary portion formed at both ends thereof having a static friction coefficient of 1.0 or more, and
(B) The charging auxiliary unit is in contact with a portion of the charging member corresponding to a non-image forming portion of the photosensitive drum.   The charging device according to claim 1, wherein the resin foam having an open cell structure is made of a melamine resin.   3. The charging device according to claim 1, wherein the resin foam having an open cell structure is heated and compressed from its original shape.   The charging device according to claim 1, wherein the follow-up auxiliary unit is made of an elastic material.   The charging device according to claim 4, wherein the elastic material is formed of an elastic material obtained by subjecting a melamine resin foam impregnated with rubber and a crosslinking agent to a crosslinking reaction treatment.   6. The charging device according to claim 1, wherein the electric resistance adjusting layer is made of a thermoplastic resin in which a polymer ion conductive agent is dispersed in a thermoplastic resin. 7. The charging device according to claim 1, wherein the electric resistivity adjusting layer has a volume specific resistance value of 10 ⁶ to 10 ⁹ Ω · cm.   The charging device according to claim 1, wherein a surface layer is provided on a surface of the electric resistance adjusting layer.   The charging device according to claim 8, wherein a resistance value of the surface layer is larger than a resistance value of the electric resistance adjusting layer.   10. A process cartridge comprising at least an image carrier for forming a latent image and a charging device, which is integrally supported and detachably fixed to a main body of the image forming device, wherein the charging device comprises: A process cartridge comprising the charging device described above.   A process cartridge; an exposure unit that exposes the surface of the image carrier to form an electrostatic latent image; a developing unit that supplies toner to the electrostatic latent image on the surface of the image carrier to visualize the image; 11. An image forming apparatus comprising at least a transfer unit that transfers a visualized image of a surface onto a transfer medium, wherein the process cartridge is constituted by the process cartridge according to claim 10.